This invention relates to methods and apparatus for enhancing the reliability of computer equipment. In particular, this invention is drawn to increasing interconnections between multiple controllers and multiple electronic devices to enhance reliability.
Large capacity mass storage subsystems are typically shared with a number of computers. Such storage subsystems can be centrally located in secure facilities that offer backup power supplies, isolation from hazards, and other features to ensure reliable access to the stored data.
The storage subsystem is made up of a plurality of storage devices such as disk drives to minimize the extent of data loss in the event of failure of a single device. Such an organization also aids throughput by distributing the location of the data across multiple storage devices. Some systems deliberately distribute the data and error correction codes across multiple storage devices in ways that permit full recovery of the data even if one or more of the devices fails.
These approaches tend to assume complete device failure. Although the risk of catastrophic failure for the system as a whole is reduced through device redundancy, the risk of failure to individual devices is not addressed. Although reliability of the system is preserved, the system efficiency tends to decrease due to the additional overhead required to recover the lost data from the error correction codes and the remaining data.
Each storage device is interconnected with a backplane in a manner that presents numerous single failure points, for example, in the power, address, data, or control paths between the backplane and the storage device. Reduction of the number of these single points of failure is desirable for the purpose of increasing the reliability of individual storage devices and therefore the efficiency of the system as a whole.
Methods and apparatus for connecting a plurality of electronic devices with corresponding backplanes to improve reliability of accessing the devices are described. In one embodiment, the apparatus includes first and second backplanes having connectors for at least one device. A device having a plurality of data paths has a first data path coupled to a data path connector of the first backplane. A second data path of the device is coupled to a data path connector of the second backplane.
One apparatus includes a plurality of electronic devices and a plurality of backplanes. Each device has a plurality of data paths. Each backplane provides connectors for the same plurality of devices. The individual data paths for each device are connected to distinct backplanes.
Another embodiment includes first and second backplanes with connectors for at least one electronic device. A Y-coupler has first and second Y-connectors coupled to a common Y-connector. The first Y-connector is connected to a data path connector of the first backplane. The second Y-connector is connected to a data path connector of the second backplane. A device data path is connected to the common device connector.
In various embodiments, the backplanes are arranged to lie in a common plane. Alternatively, the backplanes are arranged to lie in distinct parallel planes. The devices may include nonvolatile memory devices such as disk drives.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below.